I am trying to add a custiom property to an add on but it shows me an error
Spelling Error
Quite likely the property fails to register because it has no idea what discrription  is. (Most likely you are alerted to this error when trying to register the operator class) Coding is about attention to detail.  Recommend for blender coding questions here, adding minimal, but runable, code to your question eg the register code for above.
Sure enough, tacking bpy.utils.register_class(MyOperator) to the question code, and checking system console
TypeError: 'discrription' is an invalid keyword argument for FloatProperty()
ValueError: bpy_struct &quot;OBJECT_OT_my_operator&quot; registration error: noise_scale could not register

any attempt to use noise_scale with this operator will lead to error as mentioned in question.
Use description instead and will register as intended.
&gt;&gt;&gt; bpy.ops.object.my_operator(
my_operator()
bpy.ops.object.my_operator(noise_scale=1)
Tooltip